1. Field of the Invention
The present invention relates to an eyeglass lens processing apparatus for processing an eyeglass lens, and to a grinding water tank unit for storing and circulating grinding water used at the time of lens processing.
2. Description of Related Art
In an eyeglass lens processing apparatus, grinding water is supplied during processing so as to cool the ground portion of a lens and eliminate grinding debris from the lens. As this water supplying system, there is a system in which grinding water is circulated between a grinding water tank and the main body of the processing apparatus. In this system, the grinding water stored in the tank is pumped up by a pump and supplied to the main body of the processing apparatus, the grinding water after use is discharged (drained) into the tank and is reused by being circulated.
If a plastic lens is ground by a grinding wheel, the grinding water, particulates of grinding debris and air cause bubbles to be generated in the discharged grinding water. If the grinding is continued, there are cases where the bubbles and the grinding water overflow the tank, or the bubbles and the grinding water flow into the grinding chamber of the main body of the processing apparatus. For this reason, generally, anti-foaming agent (surface active agent) is mixed with the grinding water and the mixture is used in order to restrain a generation of the bubbles.
However, if using the anti-foaming agent, the grinding water tends to be turbid. If the turbid grinding water continues to be circulated and used, processing quality may deteriorate and troubles of the processing apparatus are liable to occur. Further, recently, in term of the environment issue, it becomes necessary to restrain use of surface-active agent inclusive of the anti-foaming agent. In case of no use of anti-foaming agent, since the tank is filled with the bubbles by processing a small number of lenses, replacement of grinding water in the tank should be frequently conducted.